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ATIOAL ADVISORY OO2I2T FOR ATRO:TIOS

i'To. 120

T:E CIERVA "AUTOIRO" MARK III (RITIs:-)

Armstrong—Sidcieluy "enet Majo E:.:ine

V ash I rig to ii June, 13O

https://ntrs.nasa.gov/search.jsp?R=19930090404 2020-03-22T09:47:56+00:00Z

NATIONAL ADVISORY C0I'TE FOR 'AERONAUTICS.

AIRCRAFT CIRCULAR . NO. 120.

THE CIERVA . "AUTOGIRO't MARK III (BRITISH)*

Armstrong-Siddeley "Genet, Major" Engine.

The aütogio illustrated in the photographs of this circular

is vn as the type C.19, .Iark ha (Figs. 2, 3, and 4) and is,

with minor exceptions, identical with the type that is being

put into production,, and which wiii be known as the Mark III

(Fig. i)..

In the performance test conducted at the old Avro airport

near Soi4hampton . it was emonstrated that the aircraft could be

banked .ste'eply like an ordinary airplane, and. could glide either

in a: fairly flat glide, or in.a very steep one. The "zooms" were

quita.impessive, and the climbing angle was very good (Fig. 5).

However, its rae of climb was iot as good as that of an air-

plane. . .

When some fifty or sixty yards from the hangar, the pilot

pulled the sDick back, the aircraft tilted backward. and settled

down nto.a,ve.ry steep path,. touching the ground and coming to a

standstill after something like two revolutions of the landing

wheels.. 3y gently applying the brake with which the latest type

is pov.ided the rotowas.soon stopped, and. the flight Was end-

ed. Tie pilot had takeD off vith tne rotor doing 85 r.p.m.

*Frorn Flight, Mey 9, 1930.

N.AC.A. Aircraft Circulax No. 120

Constructi-onal -Features

in the notes which type, C.19, Mask

III, may be asumed , be; refeéto .'e±cet:. *heñ' otherwise

stated.. he fl'a :, j'd .:' 'o13d stc'1' :tibê . cttr of normal,

welded construction. The forward end. terminates in an engine

plate 'for the "Gcnot'...Majo lt.;105;hp..Crin: whi'l.ö at the rear.. is

carried the. bi51ne tail . ('Fig •f ;:1This. 'onisth' of two ver.ti.c1:

fins of -wolded steel, tubes twudders.o±' duralumii., .and.twb tail.'

planes, -aIsoof 'duriuñin cnt.riioti.àn'.to which;.re:.hi'nged. .tha r .r:;,

dura1uriin . elevator flaps (Fig. 7). The control of the tall. sur.:1

,fi,aces'is-abcompli'shod .. ..s shown i.t Figure' 8. ; ...............':

The rotor' blads- are df mi,'cdcont:1.,ucton in t'.ht the .sin-'.

gl'e' 'epers :c,f. the 'rdtdr' bldë c' dircul ir' sect'ibn tel 'tubes,:

13/4 incies in dioneter. 'and 20 S.LG., of aigh-tensi.le .. ( :T..5) steel

and th rotor biade rib are of wood in th Mark II . a(experirne.n-

tal) aircraft,' but it 'is likely that-i t product.bttype. they

will be o' duralumin. The covering of the blades is fabric,, but. th €

leading edge is cdvered with plywood,'up ' .spar.(Fig. 9.).

The ribs are vey closely. spaced. (-3 in.) and all ribs are provided

with metal f1anges'sweted'tot'hC tubular; spar'. In.additioi every

third rib' 'is. bolted to-the "spar (Fig'. 10)... Owing to the close

spacing of the 'ribs; the : Iôad t be. 'carriod y each' rib ib .very.

small, an'd.thé faOtor : of safety ; previd;ed. by :the.bo.1.ting. of :e'v.ery..'

third Tib iè in the"neigth'berho'od : ' . 20... '.'.; ;: ",

In., ho experimental aircraft (Mark ha), the rotor sps

are attached to the hinges of the rotor had by fInged doup1in's.

NA4C.A. Aircraft Circular No. 120 ... .: 3.

These are. incorporated in...orde to permit t'rbiades to be set

at yarious angles of inCenbC . : so .. to 4ete'mine the ,est anglQ..1

When that angle has been. ascertained in the Mark Ma aircraft,

the rotors for the ark 1 .11 will have tiei spars joined direc.t

to the inged. joints on t1e' rotor head.. .' s

It may be r.ec.oi,1cted that in his lecture to the Royal Aero-

nautical Society, recently, Senor de la Ciervareferréd to the

addition of oth,er: hinge, perpendicular t the first, allowing

the blades to 5 I'overtake'Lac1' other, aid that the freedom thus

given ws 'he. niaxirnun which the blades could have without becom-

ing unstable. . This hinging of the blades is shown. in Figure .11.

It will, be seen that the new rotor head consists of a hollow

steel cone, to the top of which the .che .ck.c.ables are attached,

aid of.the rotor head proper, which is a forging,, running on

ball bearings, carrying the four lugs to wh1.ch the spars of the

rotor blades are hinged. Each spar has a double hinge of which

the inner is horizontal and permits the 'biae. to rise under the

action of the lift, while the outer • hinge pin •.s vertical and

permits the blade to swing slightly fore and aft in the plane of

the blades. The moving parts of. the rotor head, are lubricated

by oil from the cqnical top, which forms the, oil tank, and in

the side of which is the oil filler., cap. ', . ' . .

Those who. had an opportuni ,ty to exairiine closely the first

autogiro built in England may remember that cables ., joining one

blade to the blades on each side of .it, were fitted and that

Lj;

N..A.C.A. Aircraft Circular N0 120

small lead. bbbbjn were pl .ae.d-in:the.centers of these cables,

qetrifügal ±'ocë swinging tie bobl4ns outward and thereby put-

ting a bain aount of tension on the cables. Ln the latest

version .:the lead bobbin have been ±eplaced by crank-armed.. damp-

ers mounted on the wing spars,(Fig. io). These . dampers work

s6mewhat. bi the pi'incip1eof the shock .absorber used oi motor

cars, and the friction between their. teol..p1ats dcork discs

can be adjusted to give wha .ver.siffness i required. The

crank arms of the dampers are :desigfled as to have a certain

degree of freC 'movement.in a vertical p1ae, thus enabling them

to adjus themselves to the rising and falling of the blades.

Owlri to its ability to land very nearly vertically, the

autogiro cal1c 'for a rather exceptional landing gear, with a trav-

el long enough to absorb the shock. The telescopic. legs are at-

tached. to the'lower sár of the, fixed wing, and. two struts above

the wing brace the latter to the fuselage (Figs. 1 & 12). The

landing gear hs avery wietrac1c, and the wheels are fitted with

Bendix örake so that the aircraft can 'cc brought to a stand-

still with almost no run:at al1.

Hitherto One of the 'a±guments against the autogiro has been

that; owing 'tO the fact that the rotor cortinues to run andto

give lift after the aircraft has come to a.. sti.stil1, there is

risk 'of 'h±nhig over oi' the ground. I fact, this has happened

on more' 'than Qne •bccasio.±i... •A.,brake ' has now,,, however, been fitted

by méahs Of' which the.: rotor :: can be stopped ,ira, very short time,

N.A.C.A Aircraft Circular No,:.120: . ... :.

axd thus the risk of turning over hould 'oe:.rnaterialiy de.creased.

The Mark lIla ogirob.s.a tare:'..we.ight of 930 pounds and. the

of A. covers a goss weight.. 1400 pounds. The gasoline Ca-

pacity is 18 gal1dnnd the oil, 2-ga1lons. Cruising at a

speed of 2 •the consumpto is approximately 6 gallons

per hour, so that ti'e still air.ang isapproximately 225 miles.

As regards perormance, the top speedof the Ma±k Ia is

approximately 90 mepeh, but by "c1.atng Up" the prôduction.air-

caft it is estimated that this fie will be increased to at

least 95 m.p.h. The aircraft is able to maintain horizontal

flight at 25 m.p.h., and the vertical descent reduces the landing

run to practically nothing. The take-off can be accomplished, in

about 30 yards, and. the climbing angle is 12 degrees. The initi4

rate 0± climb is 750 feet per minute. With pilot only on board,

the ceiling is 17,000 feet, and with full load the ceiling is

still 13,000 feet.

Character is tics

Diameter of rotors at rest

Diagonal span of rotors at rest

Span of fixed planes

Chord of fixed "

Length frox propeller to fins

35 ft. 0 in.

25 II 0

20 " 6 "

2 9

If 3 U

N.A.C.A. Arcraft Circul N0 .l2Q . ..

Areas insquarefeet: .: : Four rotor blades 89.52

T9 fid planes . 42.00 .

•A.Ierons.... : ..: . 12.68

Oblique fis •. .. . 7.92

Vertical . 26.64 .... . :

• Rudders: . . • 16l • .

• . StaWlier .. . ... 14.98 . • .

Elevtor• ........ . . . 15.3? . ..

N.A.C.A. Aircraft Circular No.120 Fig.1

fi

21Q

Feet

I,

.68 D2 .' 1 _)

• 10

.98

.37

Fig.3 The autog3ro land-ing without a run.

Note that the aircraft is heading for the hangar. It pulled up a few feet from the position in whioh it is shown in the photograph, and still some 20 yards or so from the hangar.

N.A.C.A. kiroraft Circular No.120

Fige.3, 3,4,7,11,12.

V

w

L Fig.2 Three-quarter front view of the autogiro, type C.1

Mark ha. The engine is an Armstrong Siddeley "Genet Ma3orw.

;

.E 144'0$4lI'1 f0 0OVO

C 0-4 5.14. 4' .40 . 4r4P. r4

tHr4 .4 4 . 5 q0 .-44'e i)-I0OS).4 14

..4 k.0 a 0" 1-. 4' E-' -4 0 4' 42.0 0

Tig.4 In full flight.

Note the coning angle of the rotor blades.

Fig.l2 The star-board

half of the land-ing gear. Note the Bendix wheel brakes.

Fig.11 The rotor bead. The .'' flange couplings .

the spars will not be incorporated in the produc- go tion type. Below is the - conical top of the head. This serves as an oil tank. Note the filler cap on the side. On the left,tbe blank&' for the rotor head.

I.A.C.A. Airoraft Circular Io..l30 Tigs.5,6,8,9,lO.

7tg.lO So oonstruo-tiona3. details

of the autogiro: 1, a wooden rib end its attachment to tuxlar epar of rotor blade. 3, one of the daspere which oheok the ovmeot of the rotor vanes in a horisontal plane. Details of the damper are shown in 3, and the method of mounting the damper on the par is shown in 4. Details of the forkends of the rotor spars are illue-trated in 5. 6, shows the strut fitting on the fixed wing.

J3g.9 The fixed wing is of wood construc-

tion. Details of wing spar, wing ribs and dihedral wing tip are shown.

of fuselage 000structiona.l d.tails Sketch showing mounting for the biplane tail.

Tig.8 aow the d .. tail

• surfaces are :1 : I - controlled. The j : .- lower plane is I . •' , the etabiliser

• .. and the upper

•° the elevator. 1 n The lever on the

left-hand side - j (9, of the 000kpit

/ i" controls the ?'c.:'c/c.7 if' - tilting for

0' ..- starting the rotor.

Fig.5 _____ - -

angles claimed for the autogiro, which gives a. wide ohoioe of landing ground. from any particular point. The nearly vertical descent (indicated on the right of the diagram) is particularly interesting.